1. Field of the Invention
The present invention relates to a photoelectric converting apparatus of the type having a plurality of photosensors and a plurality of signal output lines for picking up signals from the photosensors, wherein the signals are picked up through signal output terminals smaller in number than that of the signal output lines.
2. Related Background Art
In order to read signals from the entirety or part of a color sensor made of a plurality of photosensors disposed one or two-dimensionally, it becomes necessary to provide a plurality of signal output lines.
FIG. 1 is a circuit diagram showing one example of a conventional photoelectric converting apparatus.
In the Figure, there are provided sensor line blocks 101 and 102 each constructed of one-dimensionally disposed photosensors Signals from each sensor line block are sequentially read via signal output lines 103 and 104 which are commonly connected to an amplifier 105 having a signal output terminal 106. During the reading of signals from one sensor line block, reading of signals from the other line sensor block is inhibited. Thus, signals from the two signal output lines can be read via the single output terminal, resulting in fewer numbers of wires for connection to external circuitry.
In operation of the above conventional photoelectric converting apparatus, signal from the sensor line blocks 101 and 102 are temporarily stored in charge storage capacitors or wiring capacitance C1 to Cn. Signals from the sensor line blocks 101 and 102 are sequentially picked up and transferred to the signal output lines 103 and 104, respectively under the control of shift registers. The signals are then outputted via the amplifier 105 at its signal output terminal 106
However, since the signal output lines 103 and 104 are connected together at the input terminal Of the amplifier, each of the wiring capacitances Cw1 and Cw2 of the signal output line are added together, resulting in a large capacitance on each signal output line. Thus, there arises a problem that the output of a signal stored, for example, in the charge storage capacitor C1 is reduced at the signal output line 103 by the large capacitance.
The above problem becomes more serious in the case of a large number of sensor lines and hence a large number of signal output lines.